1. Field of the Invention
The present invention relates to a polyamide resin composition. More particularly, the present invention relates to a polyamide resin composition which is excellent in weather resistance, moldability and mechanical properties, and which can be injection-molded.
2. Prior Art
Polyamide resins have good mechanical properties, moldability and chemical resistance and are in wide use as automobile parts, machine parts, building materials, etc. Polyamide resins, however, are very susceptible to oxidative deterioration and, when deteriorated by oxidation, reduce the polymerization degree. This reduction in polymerization degree invites undesirable phenomena such as reduction in mechanical properties, occurrence of surface cracks, coloring and the like. The oxidative deterioration is accelerated by heat or light and, therefore, use of polyamide resin in outdoor exposure is restricted.
In order to prevent the above oxidative deterioration, i.e. to improve the weather resistance of polyamide resin, addition of various stabilizers to polyamide resin is disclosed in Japanese Patent Application Kokai (Laid-Open) No. 93652/1973 and Japanese Patent Publication No. 29823/1989.
That is, Japanese Patent Application Kokai (Laid-Open) No. 93652/1973 discloses a polyamide resin composition having excellent heat resistance and light resistance, obtained by adding to a polyamide a metal complex of a tetraalkylammonium iodide represented by the following general formula ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R4 are each a hydrogen atom or an alkyl group having 1 to 5 carbon atoms and at least one of R.sub.1 to R4 is an alkyl group.
Japanese Patent Publication No. 29823/1989 discloses a reinforced polyamide molding material comprising (A) 0.01 to 5% by weight of carbon black, (B) 1 to 70% by weight of a glass fiber, and (C) 25 to 98.09% by weight of a polyamide per 100% by weight of the total amount of the components (A), (B) and (C), wherein the particle size of the carbon black is such that the maximum particle diameter is 20 .mu.m or less and the volume average particle diameter of those particles having diameters of 1 .mu.m or more is 5 .mu.m or less.
The improvement of weather resistance by the above composition or material, however, is not satisfactory, and further improvement is desired.